/*
 * Copyright (c) 1996, 2011, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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/*
 * (C) Copyright Taligent, Inc. 1996 - All Rights Reserved
 * (C) Copyright IBM Corp. 1996 - All Rights Reserved
 *
 *   The original version of this source code and documentation is copyrighted
 * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
 * materials are provided under terms of a License Agreement between Taligent
 * and Sun. This technology is protected by multiple US and International
 * patents. This notice and attribution to Taligent may not be removed.
 *   Taligent is a registered trademark of Taligent, Inc.
 *
 */

package java.util;

import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.IOException;
import sun.util.calendar.CalendarSystem;
import sun.util.calendar.CalendarUtils;
import sun.util.calendar.BaseCalendar;
import sun.util.calendar.Gregorian;

/**
 * <code>SimpleTimeZone</code> is a concrete subclass of <code>TimeZone</code>
 * that represents a time zone for use with a Gregorian calendar.
 * The class holds an offset from GMT, called <em>raw offset</em>, and start
 * and end rules for a daylight saving time schedule.  Since it only holds
 * single values for each, it cannot handle historical changes in the offset
 * from GMT and the daylight saving schedule, except that the {@link
 * #setStartYear setStartYear} method can specify the year when the daylight
 * saving time schedule starts in effect.
 * <p>
 * To construct a <code>SimpleTimeZone</code> with a daylight saving time
 * schedule, the schedule can be described with a set of rules,
 * <em>start-rule</em> and <em>end-rule</em>. A day when daylight saving time
 * starts or ends is specified by a combination of <em>month</em>,
 * <em>day-of-month</em>, and <em>day-of-week</em> values. The <em>month</em>
 * value is represented by a Calendar {@link Calendar#MONTH MONTH} field
 * value, such as {@link Calendar#MARCH}. The <em>day-of-week</em> value is
 * represented by a Calendar {@link Calendar#DAY_OF_WEEK DAY_OF_WEEK} value,
 * such as {@link Calendar#SUNDAY SUNDAY}. The meanings of value combinations
 * are as follows.
 *
 * <ul>
 * <li><b>Exact day of month</b><br>
 * To specify an exact day of month, set the <em>month</em> and
 * <em>day-of-month</em> to an exact value, and <em>day-of-week</em> to zero. For
 * example, to specify March 1, set the <em>month</em> to {@link Calendar#MARCH
 * MARCH}, <em>day-of-month</em> to 1, and <em>day-of-week</em> to 0.</li>
 *
 * <li><b>Day of week on or after day of month</b><br>
 * To specify a day of week on or after an exact day of month, set the
 * <em>month</em> to an exact month value, <em>day-of-month</em> to the day on
 * or after which the rule is applied, and <em>day-of-week</em> to a negative {@link
 * Calendar#DAY_OF_WEEK DAY_OF_WEEK} field value. For example, to specify the
 * second Sunday of April, set <em>month</em> to {@link Calendar#APRIL APRIL},
 * <em>day-of-month</em> to 8, and <em>day-of-week</em> to <code>-</code>{@link
 * Calendar#SUNDAY SUNDAY}.</li>
 *
 * <li><b>Day of week on or before day of month</b><br>
 * To specify a day of the week on or before an exact day of the month, set
 * <em>day-of-month</em> and <em>day-of-week</em> to a negative value. For
 * example, to specify the last Wednesday on or before the 21st of March, set
 * <em>month</em> to {@link Calendar#MARCH MARCH}, <em>day-of-month</em> is -21
 * and <em>day-of-week</em> is <code>-</code>{@link Calendar#WEDNESDAY WEDNESDAY}. </li>
 *
 * <li><b>Last day-of-week of month</b><br>
 * To specify, the last day-of-week of the month, set <em>day-of-week</em> to a
 * {@link Calendar#DAY_OF_WEEK DAY_OF_WEEK} value and <em>day-of-month</em> to
 * -1. For example, to specify the last Sunday of October, set <em>month</em>
 * to {@link Calendar#OCTOBER OCTOBER}, <em>day-of-week</em> to {@link
 * Calendar#SUNDAY SUNDAY} and <em>day-of-month</em> to -1.  </li>
 *
 * </ul>
 * The time of the day at which daylight saving time starts or ends is
 * specified by a millisecond value within the day. There are three kinds of
 * <em>mode</em>s to specify the time: {@link #WALL_TIME}, {@link
 * #STANDARD_TIME} and {@link #UTC_TIME}. For example, if daylight
 * saving time ends
 * at 2:00 am in the wall clock time, it can be specified by 7200000
 * milliseconds in the {@link #WALL_TIME} mode. In this case, the wall clock time
 * for an <em>end-rule</em> means the same thing as the daylight time.
 * <p>
 * The following are examples of parameters for constructing time zone objects.
 * <pre><code>
 *      // Base GMT offset: -8:00
 *      // DST starts:      at 2:00am in standard time
 *      //                  on the first Sunday in April
 *      // DST ends:        at 2:00am in daylight time
 *      //                  on the last Sunday in October
 *      // Save:            1 hour
 *      SimpleTimeZone(-28800000,
 *                     "America/Los_Angeles",
 *                     Calendar.APRIL, 1, -Calendar.SUNDAY,
 *                     7200000,
 *                     Calendar.OCTOBER, -1, Calendar.SUNDAY,
 *                     7200000,
 *                     3600000)
 *
 *      // Base GMT offset: +1:00
 *      // DST starts:      at 1:00am in UTC time
 *      //                  on the last Sunday in March
 *      // DST ends:        at 1:00am in UTC time
 *      //                  on the last Sunday in October
 *      // Save:            1 hour
 *      SimpleTimeZone(3600000,
 *                     "Europe/Paris",
 *                     Calendar.MARCH, -1, Calendar.SUNDAY,
 *                     3600000, SimpleTimeZone.UTC_TIME,
 *                     Calendar.OCTOBER, -1, Calendar.SUNDAY,
 *                     3600000, SimpleTimeZone.UTC_TIME,
 *                     3600000)
 * </code></pre>
 * These parameter rules are also applicable to the set rule methods, such as
 * <code>setStartRule</code>.
 *
 * @author David Goldsmith, Mark Davis, Chen-Lieh Huang, Alan Liu
 * @see Calendar
 * @see GregorianCalendar
 * @see TimeZone
 * @since 1.1
 */

public class SimpleTimeZone extends TimeZone {

  /**
   * Constructs a SimpleTimeZone with the given base time zone offset from GMT
   * and time zone ID with no daylight saving time schedule.
   *
   * @param rawOffset The base time zone offset in milliseconds to GMT.
   * @param ID The time zone name that is given to this instance.
   */
  public SimpleTimeZone(int rawOffset, String ID) {
    this.rawOffset = rawOffset;
    setID(ID);
    dstSavings = millisPerHour; // In case user sets rules later
  }

  /**
   * Constructs a SimpleTimeZone with the given base time zone offset from
   * GMT, time zone ID, and rules for starting and ending the daylight
   * time.
   * Both <code>startTime</code> and <code>endTime</code> are specified to be
   * represented in the wall clock time. The amount of daylight saving is
   * assumed to be 3600000 milliseconds (i.e., one hour). This constructor is
   * equivalent to:
   * <pre><code>
   *     SimpleTimeZone(rawOffset,
   *                    ID,
   *                    startMonth,
   *                    startDay,
   *                    startDayOfWeek,
   *                    startTime,
   *                    SimpleTimeZone.{@link #WALL_TIME},
   *                    endMonth,
   *                    endDay,
   *                    endDayOfWeek,
   *                    endTime,
   *                    SimpleTimeZone.{@link #WALL_TIME},
   *                    3600000)
   * </code></pre>
   *
   * @param rawOffset The given base time zone offset from GMT.
   * @param ID The time zone ID which is given to this object.
   * @param startMonth The daylight saving time starting month. Month is a {@link Calendar#MONTH
   * MONTH} field value (0-based. e.g., 0 for January).
   * @param startDay The day of the month on which the daylight saving time starts. See the class
   * description for the special cases of this parameter.
   * @param startDayOfWeek The daylight saving time starting day-of-week. See the class description
   * for the special cases of this parameter.
   * @param startTime The daylight saving time starting time in local wall clock time (in
   * milliseconds within the day), which is local standard time in this case.
   * @param endMonth The daylight saving time ending month. Month is a {@link Calendar#MONTH MONTH}
   * field value (0-based. e.g., 9 for October).
   * @param endDay The day of the month on which the daylight saving time ends. See the class
   * description for the special cases of this parameter.
   * @param endDayOfWeek The daylight saving time ending day-of-week. See the class description for
   * the special cases of this parameter.
   * @param endTime The daylight saving ending time in local wall clock time, (in milliseconds
   * within the day) which is local daylight time in this case.
   * @throws IllegalArgumentException if the month, day, dayOfWeek, or time parameters are out of
   * range for the start or end rule
   */
  public SimpleTimeZone(int rawOffset, String ID,
      int startMonth, int startDay, int startDayOfWeek, int startTime,
      int endMonth, int endDay, int endDayOfWeek, int endTime) {
    this(rawOffset, ID,
        startMonth, startDay, startDayOfWeek, startTime, WALL_TIME,
        endMonth, endDay, endDayOfWeek, endTime, WALL_TIME,
        millisPerHour);
  }

  /**
   * Constructs a SimpleTimeZone with the given base time zone offset from
   * GMT, time zone ID, and rules for starting and ending the daylight
   * time.
   * Both <code>startTime</code> and <code>endTime</code> are assumed to be
   * represented in the wall clock time. This constructor is equivalent to:
   * <pre><code>
   *     SimpleTimeZone(rawOffset,
   *                    ID,
   *                    startMonth,
   *                    startDay,
   *                    startDayOfWeek,
   *                    startTime,
   *                    SimpleTimeZone.{@link #WALL_TIME},
   *                    endMonth,
   *                    endDay,
   *                    endDayOfWeek,
   *                    endTime,
   *                    SimpleTimeZone.{@link #WALL_TIME},
   *                    dstSavings)
   * </code></pre>
   *
   * @param rawOffset The given base time zone offset from GMT.
   * @param ID The time zone ID which is given to this object.
   * @param startMonth The daylight saving time starting month. Month is a {@link Calendar#MONTH
   * MONTH} field value (0-based. e.g., 0 for January).
   * @param startDay The day of the month on which the daylight saving time starts. See the class
   * description for the special cases of this parameter.
   * @param startDayOfWeek The daylight saving time starting day-of-week. See the class description
   * for the special cases of this parameter.
   * @param startTime The daylight saving time starting time in local wall clock time, which is
   * local standard time in this case.
   * @param endMonth The daylight saving time ending month. Month is a {@link Calendar#MONTH MONTH}
   * field value (0-based. e.g., 9 for October).
   * @param endDay The day of the month on which the daylight saving time ends. See the class
   * description for the special cases of this parameter.
   * @param endDayOfWeek The daylight saving time ending day-of-week. See the class description for
   * the special cases of this parameter.
   * @param endTime The daylight saving ending time in local wall clock time, which is local
   * daylight time in this case.
   * @param dstSavings The amount of time in milliseconds saved during daylight saving time.
   * @throws IllegalArgumentException if the month, day, dayOfWeek, or time parameters are out of
   * range for the start or end rule
   * @since 1.2
   */
  public SimpleTimeZone(int rawOffset, String ID,
      int startMonth, int startDay, int startDayOfWeek, int startTime,
      int endMonth, int endDay, int endDayOfWeek, int endTime,
      int dstSavings) {
    this(rawOffset, ID,
        startMonth, startDay, startDayOfWeek, startTime, WALL_TIME,
        endMonth, endDay, endDayOfWeek, endTime, WALL_TIME,
        dstSavings);
  }

  /**
   * Constructs a SimpleTimeZone with the given base time zone offset from
   * GMT, time zone ID, and rules for starting and ending the daylight
   * time.
   * This constructor takes the full set of the start and end rules
   * parameters, including modes of <code>startTime</code> and
   * <code>endTime</code>. The mode specifies either {@link #WALL_TIME wall
   * time} or {@link #STANDARD_TIME standard time} or {@link #UTC_TIME UTC
   * time}.
   *
   * @param rawOffset The given base time zone offset from GMT.
   * @param ID The time zone ID which is given to this object.
   * @param startMonth The daylight saving time starting month. Month is a {@link Calendar#MONTH
   * MONTH} field value (0-based. e.g., 0 for January).
   * @param startDay The day of the month on which the daylight saving time starts. See the class
   * description for the special cases of this parameter.
   * @param startDayOfWeek The daylight saving time starting day-of-week. See the class description
   * for the special cases of this parameter.
   * @param startTime The daylight saving time starting time in the time mode specified by
   * <code>startTimeMode</code>.
   * @param startTimeMode The mode of the start time specified by startTime.
   * @param endMonth The daylight saving time ending month. Month is a {@link Calendar#MONTH MONTH}
   * field value (0-based. e.g., 9 for October).
   * @param endDay The day of the month on which the daylight saving time ends. See the class
   * description for the special cases of this parameter.
   * @param endDayOfWeek The daylight saving time ending day-of-week. See the class description for
   * the special cases of this parameter.
   * @param endTime The daylight saving ending time in time time mode specified by
   * <code>endTimeMode</code>.
   * @param endTimeMode The mode of the end time specified by endTime
   * @param dstSavings The amount of time in milliseconds saved during daylight saving time.
   * @throws IllegalArgumentException if the month, day, dayOfWeek, time more, or time parameters
   * are out of range for the start or end rule, or if a time mode value is invalid.
   * @see #WALL_TIME
   * @see #STANDARD_TIME
   * @see #UTC_TIME
   * @since 1.4
   */
  public SimpleTimeZone(int rawOffset, String ID,
      int startMonth, int startDay, int startDayOfWeek,
      int startTime, int startTimeMode,
      int endMonth, int endDay, int endDayOfWeek,
      int endTime, int endTimeMode,
      int dstSavings) {

    setID(ID);
    this.rawOffset = rawOffset;
    this.startMonth = startMonth;
    this.startDay = startDay;
    this.startDayOfWeek = startDayOfWeek;
    this.startTime = startTime;
    this.startTimeMode = startTimeMode;
    this.endMonth = endMonth;
    this.endDay = endDay;
    this.endDayOfWeek = endDayOfWeek;
    this.endTime = endTime;
    this.endTimeMode = endTimeMode;
    this.dstSavings = dstSavings;

    // this.useDaylight is set by decodeRules
    decodeRules();
    if (dstSavings <= 0) {
      throw new IllegalArgumentException("Illegal daylight saving value: " + dstSavings);
    }
  }

  /**
   * Sets the daylight saving time starting year.
   *
   * @param year The daylight saving starting year.
   */
  public void setStartYear(int year) {
    startYear = year;
    invalidateCache();
  }

  /**
   * Sets the daylight saving time start rule. For example, if daylight saving
   * time starts on the first Sunday in April at 2 am in local wall clock
   * time, you can set the start rule by calling:
   * <pre><code>setStartRule(Calendar.APRIL, 1, Calendar.SUNDAY, 2*60*60*1000);</code></pre>
   *
   * @param startMonth The daylight saving time starting month. Month is a {@link Calendar#MONTH
   * MONTH} field value (0-based. e.g., 0 for January).
   * @param startDay The day of the month on which the daylight saving time starts. See the class
   * description for the special cases of this parameter.
   * @param startDayOfWeek The daylight saving time starting day-of-week. See the class description
   * for the special cases of this parameter.
   * @param startTime The daylight saving time starting time in local wall clock time, which is
   * local standard time in this case.
   * @throws IllegalArgumentException if the <code>startMonth</code>, <code>startDay</code>,
   * <code>startDayOfWeek</code>, or <code>startTime</code> parameters are out of range
   */
  public void setStartRule(int startMonth, int startDay, int startDayOfWeek, int startTime) {
    this.startMonth = startMonth;
    this.startDay = startDay;
    this.startDayOfWeek = startDayOfWeek;
    this.startTime = startTime;
    startTimeMode = WALL_TIME;
    decodeStartRule();
    invalidateCache();
  }

  /**
   * Sets the daylight saving time start rule to a fixed date within a month.
   * This method is equivalent to:
   * <pre><code>setStartRule(startMonth, startDay, 0, startTime)</code></pre>
   *
   * @param startMonth The daylight saving time starting month. Month is a {@link Calendar#MONTH
   * MONTH} field value (0-based. e.g., 0 for January).
   * @param startDay The day of the month on which the daylight saving time starts.
   * @param startTime The daylight saving time starting time in local wall clock time, which is
   * local standard time in this case. See the class description for the special cases of this
   * parameter.
   * @throws IllegalArgumentException if the <code>startMonth</code>, <code>startDayOfMonth</code>,
   * or <code>startTime</code> parameters are out of range
   * @since 1.2
   */
  public void setStartRule(int startMonth, int startDay, int startTime) {
    setStartRule(startMonth, startDay, 0, startTime);
  }

  /**
   * Sets the daylight saving time start rule to a weekday before or after the given date within
   * a month, e.g., the first Monday on or after the 8th.
   *
   * @param startMonth The daylight saving time starting month. Month is a {@link Calendar#MONTH
   * MONTH} field value (0-based. e.g., 0 for January).
   * @param startDay The day of the month on which the daylight saving time starts.
   * @param startDayOfWeek The daylight saving time starting day-of-week.
   * @param startTime The daylight saving time starting time in local wall clock time, which is
   * local standard time in this case.
   * @param after If true, this rule selects the first <code>dayOfWeek</code> on or <em>after</em>
   * <code>dayOfMonth</code>.  If false, this rule selects the last <code>dayOfWeek</code> on or
   * <em>before</em> <code>dayOfMonth</code>.
   * @throws IllegalArgumentException if the <code>startMonth</code>, <code>startDay</code>,
   * <code>startDayOfWeek</code>, or <code>startTime</code> parameters are out of range
   * @since 1.2
   */
  public void setStartRule(int startMonth, int startDay, int startDayOfWeek,
      int startTime, boolean after) {
    // TODO: this method doesn't check the initial values of dayOfMonth or dayOfWeek.
    if (after) {
      setStartRule(startMonth, startDay, -startDayOfWeek, startTime);
    } else {
      setStartRule(startMonth, -startDay, -startDayOfWeek, startTime);
    }
  }

  /**
   * Sets the daylight saving time end rule. For example, if daylight saving time
   * ends on the last Sunday in October at 2 am in wall clock time,
   * you can set the end rule by calling:
   * <code>setEndRule(Calendar.OCTOBER, -1, Calendar.SUNDAY, 2*60*60*1000);</code>
   *
   * @param endMonth The daylight saving time ending month. Month is a {@link Calendar#MONTH MONTH}
   * field value (0-based. e.g., 9 for October).
   * @param endDay The day of the month on which the daylight saving time ends. See the class
   * description for the special cases of this parameter.
   * @param endDayOfWeek The daylight saving time ending day-of-week. See the class description for
   * the special cases of this parameter.
   * @param endTime The daylight saving ending time in local wall clock time, (in milliseconds
   * within the day) which is local daylight time in this case.
   * @throws IllegalArgumentException if the <code>endMonth</code>, <code>endDay</code>,
   * <code>endDayOfWeek</code>, or <code>endTime</code> parameters are out of range
   */
  public void setEndRule(int endMonth, int endDay, int endDayOfWeek,
      int endTime) {
    this.endMonth = endMonth;
    this.endDay = endDay;
    this.endDayOfWeek = endDayOfWeek;
    this.endTime = endTime;
    this.endTimeMode = WALL_TIME;
    decodeEndRule();
    invalidateCache();
  }

  /**
   * Sets the daylight saving time end rule to a fixed date within a month.
   * This method is equivalent to:
   * <pre><code>setEndRule(endMonth, endDay, 0, endTime)</code></pre>
   *
   * @param endMonth The daylight saving time ending month. Month is a {@link Calendar#MONTH MONTH}
   * field value (0-based. e.g., 9 for October).
   * @param endDay The day of the month on which the daylight saving time ends.
   * @param endTime The daylight saving ending time in local wall clock time, (in milliseconds
   * within the day) which is local daylight time in this case.
   * @throws IllegalArgumentException the <code>endMonth</code>, <code>endDay</code>, or
   * <code>endTime</code> parameters are out of range
   * @since 1.2
   */
  public void setEndRule(int endMonth, int endDay, int endTime) {
    setEndRule(endMonth, endDay, 0, endTime);
  }

  /**
   * Sets the daylight saving time end rule to a weekday before or after the given date within
   * a month, e.g., the first Monday on or after the 8th.
   *
   * @param endMonth The daylight saving time ending month. Month is a {@link Calendar#MONTH MONTH}
   * field value (0-based. e.g., 9 for October).
   * @param endDay The day of the month on which the daylight saving time ends.
   * @param endDayOfWeek The daylight saving time ending day-of-week.
   * @param endTime The daylight saving ending time in local wall clock time, (in milliseconds
   * within the day) which is local daylight time in this case.
   * @param after If true, this rule selects the first <code>endDayOfWeek</code> on or
   * <em>after</em> <code>endDay</code>.  If false, this rule selects the last
   * <code>endDayOfWeek</code> on or before <code>endDay</code> of the month.
   * @throws IllegalArgumentException the <code>endMonth</code>, <code>endDay</code>,
   * <code>endDayOfWeek</code>, or <code>endTime</code> parameters are out of range
   * @since 1.2
   */
  public void setEndRule(int endMonth, int endDay, int endDayOfWeek, int endTime, boolean after) {
    if (after) {
      setEndRule(endMonth, endDay, -endDayOfWeek, endTime);
    } else {
      setEndRule(endMonth, -endDay, -endDayOfWeek, endTime);
    }
  }

  /**
   * Returns the offset of this time zone from UTC at the given
   * time. If daylight saving time is in effect at the given time,
   * the offset value is adjusted with the amount of daylight
   * saving.
   *
   * @param date the time at which the time zone offset is found
   * @return the amount of time in milliseconds to add to UTC to get local time.
   * @since 1.4
   */
  public int getOffset(long date) {
    return getOffsets(date, null);
  }

  /**
   * @see TimeZone#getOffsets
   */
  int getOffsets(long date, int[] offsets) {
    int offset = rawOffset;

    computeOffset:
    if (useDaylight) {
      synchronized (this) {
        if (cacheStart != 0) {
          if (date >= cacheStart && date < cacheEnd) {
            offset += dstSavings;
            break computeOffset;
          }
        }
      }
      BaseCalendar cal = date >= GregorianCalendar.DEFAULT_GREGORIAN_CUTOVER ?
          gcal : (BaseCalendar) CalendarSystem.forName("julian");
      BaseCalendar.Date cdate = (BaseCalendar.Date) cal.newCalendarDate(TimeZone.NO_TIMEZONE);
      // Get the year in local time
      cal.getCalendarDate(date + rawOffset, cdate);
      int year = cdate.getNormalizedYear();
      if (year >= startYear) {
        // Clear time elements for the transition calculations
        cdate.setTimeOfDay(0, 0, 0, 0);
        offset = getOffset(cal, cdate, year, date);
      }
    }

    if (offsets != null) {
      offsets[0] = rawOffset;
      offsets[1] = offset - rawOffset;
    }
    return offset;
  }

  /**
   * Returns the difference in milliseconds between local time and
   * UTC, taking into account both the raw offset and the effect of
   * daylight saving, for the specified date and time.  This method
   * assumes that the start and end month are distinct.  It also
   * uses a default {@link GregorianCalendar} object as its
   * underlying calendar, such as for determining leap years.  Do
   * not use the result of this method with a calendar other than a
   * default <code>GregorianCalendar</code>.
   *
   * <p><em>Note:  In general, clients should use
   * <code>Calendar.get(ZONE_OFFSET) + Calendar.get(DST_OFFSET)</code>
   * instead of calling this method.</em>
   *
   * @param era The era of the given date.
   * @param year The year in the given date.
   * @param month The month in the given date. Month is 0-based. e.g., 0 for January.
   * @param day The day-in-month of the given date.
   * @param dayOfWeek The day-of-week of the given date.
   * @param millis The milliseconds in day in <em>standard</em> local time.
   * @return The milliseconds to add to UTC to get local time.
   * @throws IllegalArgumentException the <code>era</code>, <code>month</code>, <code>day</code>,
   * <code>dayOfWeek</code>, or <code>millis</code> parameters are out of range
   */
  public int getOffset(int era, int year, int month, int day, int dayOfWeek,
      int millis) {
    if (era != GregorianCalendar.AD && era != GregorianCalendar.BC) {
      throw new IllegalArgumentException("Illegal era " + era);
    }

    int y = year;
    if (era == GregorianCalendar.BC) {
      // adjust y with the GregorianCalendar-style year numbering.
      y = 1 - y;
    }

    // If the year isn't representable with the 64-bit long
    // integer in milliseconds, convert the year to an
    // equivalent year. This is required to pass some JCK test cases
    // which are actually useless though because the specified years
    // can't be supported by the Java time system.
    if (y >= 292278994) {
      y = 2800 + y % 2800;
    } else if (y <= -292269054) {
      // y %= 28 also produces an equivalent year, but positive
      // year numbers would be convenient to use the UNIX cal
      // command.
      y = (int) CalendarUtils.mod((long) y, 28);
    }

    // convert year to its 1-based month value
    int m = month + 1;

    // First, calculate time as a Gregorian date.
    BaseCalendar cal = gcal;
    BaseCalendar.Date cdate = (BaseCalendar.Date) cal.newCalendarDate(TimeZone.NO_TIMEZONE);
    cdate.setDate(y, m, day);
    long time = cal.getTime(cdate); // normalize cdate
    time += millis - rawOffset; // UTC time

    // If the time value represents a time before the default
    // Gregorian cutover, recalculate time using the Julian
    // calendar system. For the Julian calendar system, the
    // normalized year numbering is ..., -2 (BCE 2), -1 (BCE 1),
    // 1, 2 ... which is different from the GregorianCalendar
    // style year numbering (..., -1, 0 (BCE 1), 1, 2, ...).
    if (time < GregorianCalendar.DEFAULT_GREGORIAN_CUTOVER) {
      cal = (BaseCalendar) CalendarSystem.forName("julian");
      cdate = (BaseCalendar.Date) cal.newCalendarDate(TimeZone.NO_TIMEZONE);
      cdate.setNormalizedDate(y, m, day);
      time = cal.getTime(cdate) + millis - rawOffset;
    }

    if ((cdate.getNormalizedYear() != y)
        || (cdate.getMonth() != m)
        || (cdate.getDayOfMonth() != day)
        // The validation should be cdate.getDayOfWeek() ==
        // dayOfWeek. However, we don't check dayOfWeek for
        // compatibility.
        || (dayOfWeek < Calendar.SUNDAY || dayOfWeek > Calendar.SATURDAY)
        || (millis < 0 || millis >= (24 * 60 * 60 * 1000))) {
      throw new IllegalArgumentException();
    }

    if (!useDaylight || year < startYear || era != GregorianCalendar.CE) {
      return rawOffset;
    }

    return getOffset(cal, cdate, y, time);
  }

  private int getOffset(BaseCalendar cal, BaseCalendar.Date cdate, int year, long time) {
    synchronized (this) {
      if (cacheStart != 0) {
        if (time >= cacheStart && time < cacheEnd) {
          return rawOffset + dstSavings;
        }
        if (year == cacheYear) {
          return rawOffset;
        }
      }
    }

    long start = getStart(cal, cdate, year);
    long end = getEnd(cal, cdate, year);
    int offset = rawOffset;
    if (start <= end) {
      if (time >= start && time < end) {
        offset += dstSavings;
      }
      synchronized (this) {
        cacheYear = year;
        cacheStart = start;
        cacheEnd = end;
      }
    } else {
      if (time < end) {
        // TODO: support Gregorian cutover. The previous year
        // may be in the other calendar system.
        start = getStart(cal, cdate, year - 1);
        if (time >= start) {
          offset += dstSavings;
        }
      } else if (time >= start) {
        // TODO: support Gregorian cutover. The next year
        // may be in the other calendar system.
        end = getEnd(cal, cdate, year + 1);
        if (time < end) {
          offset += dstSavings;
        }
      }
      if (start <= end) {
        synchronized (this) {
          // The start and end transitions are in multiple years.
          cacheYear = (long) startYear - 1;
          cacheStart = start;
          cacheEnd = end;
        }
      }
    }
    return offset;
  }

  private long getStart(BaseCalendar cal, BaseCalendar.Date cdate, int year) {
    int time = startTime;
    if (startTimeMode != UTC_TIME) {
      time -= rawOffset;
    }
    return getTransition(cal, cdate, startMode, year, startMonth, startDay,
        startDayOfWeek, time);
  }

  private long getEnd(BaseCalendar cal, BaseCalendar.Date cdate, int year) {
    int time = endTime;
    if (endTimeMode != UTC_TIME) {
      time -= rawOffset;
    }
    if (endTimeMode == WALL_TIME) {
      time -= dstSavings;
    }
    return getTransition(cal, cdate, endMode, year, endMonth, endDay,
        endDayOfWeek, time);
  }

  private long getTransition(BaseCalendar cal, BaseCalendar.Date cdate,
      int mode, int year, int month, int dayOfMonth,
      int dayOfWeek, int timeOfDay) {
    cdate.setNormalizedYear(year);
    cdate.setMonth(month + 1);
    switch (mode) {
      case DOM_MODE:
        cdate.setDayOfMonth(dayOfMonth);
        break;

      case DOW_IN_MONTH_MODE:
        cdate.setDayOfMonth(1);
        if (dayOfMonth < 0) {
          cdate.setDayOfMonth(cal.getMonthLength(cdate));
        }
        cdate = (BaseCalendar.Date) cal.getNthDayOfWeek(dayOfMonth, dayOfWeek, cdate);
        break;

      case DOW_GE_DOM_MODE:
        cdate.setDayOfMonth(dayOfMonth);
        cdate = (BaseCalendar.Date) cal.getNthDayOfWeek(1, dayOfWeek, cdate);
        break;

      case DOW_LE_DOM_MODE:
        cdate.setDayOfMonth(dayOfMonth);
        cdate = (BaseCalendar.Date) cal.getNthDayOfWeek(-1, dayOfWeek, cdate);
        break;
    }
    return cal.getTime(cdate) + timeOfDay;
  }

  /**
   * Gets the GMT offset for this time zone.
   *
   * @return the GMT offset value in milliseconds
   * @see #setRawOffset
   */
  public int getRawOffset() {
    // The given date will be taken into account while
    // we have the historical time zone data in place.
    return rawOffset;
  }

  /**
   * Sets the base time zone offset to GMT.
   * This is the offset to add to UTC to get local time.
   *
   * @see #getRawOffset
   */
  public void setRawOffset(int offsetMillis) {
    this.rawOffset = offsetMillis;
  }

  /**
   * Sets the amount of time in milliseconds that the clock is advanced
   * during daylight saving time.
   *
   * @param millisSavedDuringDST the number of milliseconds the time is advanced with respect to
   * standard time when the daylight saving time rules are in effect. A positive number, typically
   * one hour (3600000).
   * @see #getDSTSavings
   * @since 1.2
   */
  public void setDSTSavings(int millisSavedDuringDST) {
    if (millisSavedDuringDST <= 0) {
      throw new IllegalArgumentException("Illegal daylight saving value: "
          + millisSavedDuringDST);
    }
    dstSavings = millisSavedDuringDST;
  }

  /**
   * Returns the amount of time in milliseconds that the clock is
   * advanced during daylight saving time.
   *
   * @return the number of milliseconds the time is advanced with respect to standard time when the
   * daylight saving rules are in effect, or 0 (zero) if this time zone doesn't observe daylight
   * saving time.
   * @see #setDSTSavings
   * @since 1.2
   */
  public int getDSTSavings() {
    return useDaylight ? dstSavings : 0;
  }

  /**
   * Queries if this time zone uses daylight saving time.
   *
   * @return true if this time zone uses daylight saving time; false otherwise.
   */
  public boolean useDaylightTime() {
    return useDaylight;
  }

  /**
   * Returns {@code true} if this {@code SimpleTimeZone} observes
   * Daylight Saving Time. This method is equivalent to {@link
   * #useDaylightTime()}.
   *
   * @return {@code true} if this {@code SimpleTimeZone} observes Daylight Saving Time; {@code
   * false} otherwise.
   * @since 1.7
   */
  @Override
  public boolean observesDaylightTime() {
    return useDaylightTime();
  }

  /**
   * Queries if the given date is in daylight saving time.
   *
   * @return true if daylight saving time is in effective at the given date; false otherwise.
   */
  public boolean inDaylightTime(Date date) {
    return (getOffset(date.getTime()) != rawOffset);
  }

  /**
   * Returns a clone of this <code>SimpleTimeZone</code> instance.
   *
   * @return a clone of this instance.
   */
  public Object clone() {
    return super.clone();
  }

  /**
   * Generates the hash code for the SimpleDateFormat object.
   *
   * @return the hash code for this object
   */
  public synchronized int hashCode() {
    return startMonth ^ startDay ^ startDayOfWeek ^ startTime ^
        endMonth ^ endDay ^ endDayOfWeek ^ endTime ^ rawOffset;
  }

  /**
   * Compares the equality of two <code>SimpleTimeZone</code> objects.
   *
   * @param obj The <code>SimpleTimeZone</code> object to be compared with.
   * @return True if the given <code>obj</code> is the same as this <code>SimpleTimeZone</code>
   * object; false otherwise.
   */
  public boolean equals(Object obj) {
    if (this == obj) {
      return true;
    }
    if (!(obj instanceof SimpleTimeZone)) {
      return false;
    }

    SimpleTimeZone that = (SimpleTimeZone) obj;

    return getID().equals(that.getID()) &&
        hasSameRules(that);
  }

  /**
   * Returns <code>true</code> if this zone has the same rules and offset as another zone.
   *
   * @param other the TimeZone object to be compared with
   * @return <code>true</code> if the given zone is a SimpleTimeZone and has the same rules and
   * offset as this one
   * @since 1.2
   */
  public boolean hasSameRules(TimeZone other) {
    if (this == other) {
      return true;
    }
    if (!(other instanceof SimpleTimeZone)) {
      return false;
    }
    SimpleTimeZone that = (SimpleTimeZone) other;
    return rawOffset == that.rawOffset &&
        useDaylight == that.useDaylight &&
        (!useDaylight
            // Only check rules if using DST
            || (dstSavings == that.dstSavings &&
            startMode == that.startMode &&
            startMonth == that.startMonth &&
            startDay == that.startDay &&
            startDayOfWeek == that.startDayOfWeek &&
            startTime == that.startTime &&
            startTimeMode == that.startTimeMode &&
            endMode == that.endMode &&
            endMonth == that.endMonth &&
            endDay == that.endDay &&
            endDayOfWeek == that.endDayOfWeek &&
            endTime == that.endTime &&
            endTimeMode == that.endTimeMode &&
            startYear == that.startYear));
  }

  /**
   * Returns a string representation of this time zone.
   *
   * @return a string representation of this time zone.
   */
  public String toString() {
    return getClass().getName() +
        "[id=" + getID() +
        ",offset=" + rawOffset +
        ",dstSavings=" + dstSavings +
        ",useDaylight=" + useDaylight +
        ",startYear=" + startYear +
        ",startMode=" + startMode +
        ",startMonth=" + startMonth +
        ",startDay=" + startDay +
        ",startDayOfWeek=" + startDayOfWeek +
        ",startTime=" + startTime +
        ",startTimeMode=" + startTimeMode +
        ",endMode=" + endMode +
        ",endMonth=" + endMonth +
        ",endDay=" + endDay +
        ",endDayOfWeek=" + endDayOfWeek +
        ",endTime=" + endTime +
        ",endTimeMode=" + endTimeMode + ']';
  }

  // =======================privates===============================

  /**
   * The month in which daylight saving time starts.  This value must be
   * between <code>Calendar.JANUARY</code> and
   * <code>Calendar.DECEMBER</code> inclusive.  This value must not equal
   * <code>endMonth</code>.
   * <p>If <code>useDaylight</code> is false, this value is ignored.
   *
   * @serial
   */
  private int startMonth;

  /**
   * This field has two possible interpretations:
   * <dl>
   * <dt><code>startMode == DOW_IN_MONTH</code></dt>
   * <dd>
   * <code>startDay</code> indicates the day of the month of
   * <code>startMonth</code> on which daylight
   * saving time starts, from 1 to 28, 30, or 31, depending on the
   * <code>startMonth</code>.
   * </dd>
   * <dt><code>startMode != DOW_IN_MONTH</code></dt>
   * <dd>
   * <code>startDay</code> indicates which <code>startDayOfWeek</code> in the
   * month <code>startMonth</code> daylight
   * saving time starts on.  For example, a value of +1 and a
   * <code>startDayOfWeek</code> of <code>Calendar.SUNDAY</code> indicates the
   * first Sunday of <code>startMonth</code>.  Likewise, +2 would indicate the
   * second Sunday, and -1 the last Sunday.  A value of 0 is illegal.
   * </dd>
   * </dl>
   * <p>If <code>useDaylight</code> is false, this value is ignored.
   *
   * @serial
   */
  private int startDay;

  /**
   * The day of the week on which daylight saving time starts.  This value
   * must be between <code>Calendar.SUNDAY</code> and
   * <code>Calendar.SATURDAY</code> inclusive.
   * <p>If <code>useDaylight</code> is false or
   * <code>startMode == DAY_OF_MONTH</code>, this value is ignored.
   *
   * @serial
   */
  private int startDayOfWeek;

  /**
   * The time in milliseconds after midnight at which daylight saving
   * time starts.  This value is expressed as wall time, standard time,
   * or UTC time, depending on the setting of <code>startTimeMode</code>.
   * <p>If <code>useDaylight</code> is false, this value is ignored.
   *
   * @serial
   */
  private int startTime;

  /**
   * The format of startTime, either WALL_TIME, STANDARD_TIME, or UTC_TIME.
   *
   * @serial
   * @since 1.3
   */
  private int startTimeMode;

  /**
   * The month in which daylight saving time ends.  This value must be
   * between <code>Calendar.JANUARY</code> and
   * <code>Calendar.UNDECIMBER</code>.  This value must not equal
   * <code>startMonth</code>.
   * <p>If <code>useDaylight</code> is false, this value is ignored.
   *
   * @serial
   */
  private int endMonth;

  /**
   * This field has two possible interpretations:
   * <dl>
   * <dt><code>endMode == DOW_IN_MONTH</code></dt>
   * <dd>
   * <code>endDay</code> indicates the day of the month of
   * <code>endMonth</code> on which daylight
   * saving time ends, from 1 to 28, 30, or 31, depending on the
   * <code>endMonth</code>.
   * </dd>
   * <dt><code>endMode != DOW_IN_MONTH</code></dt>
   * <dd>
   * <code>endDay</code> indicates which <code>endDayOfWeek</code> in th
   * month <code>endMonth</code> daylight
   * saving time ends on.  For example, a value of +1 and a
   * <code>endDayOfWeek</code> of <code>Calendar.SUNDAY</code> indicates the
   * first Sunday of <code>endMonth</code>.  Likewise, +2 would indicate the
   * second Sunday, and -1 the last Sunday.  A value of 0 is illegal.
   * </dd>
   * </dl>
   * <p>If <code>useDaylight</code> is false, this value is ignored.
   *
   * @serial
   */
  private int endDay;

  /**
   * The day of the week on which daylight saving time ends.  This value
   * must be between <code>Calendar.SUNDAY</code> and
   * <code>Calendar.SATURDAY</code> inclusive.
   * <p>If <code>useDaylight</code> is false or
   * <code>endMode == DAY_OF_MONTH</code>, this value is ignored.
   *
   * @serial
   */
  private int endDayOfWeek;

  /**
   * The time in milliseconds after midnight at which daylight saving
   * time ends.  This value is expressed as wall time, standard time,
   * or UTC time, depending on the setting of <code>endTimeMode</code>.
   * <p>If <code>useDaylight</code> is false, this value is ignored.
   *
   * @serial
   */
  private int endTime;

  /**
   * The format of endTime, either <code>WALL_TIME</code>,
   * <code>STANDARD_TIME</code>, or <code>UTC_TIME</code>.
   *
   * @serial
   * @since 1.3
   */
  private int endTimeMode;

  /**
   * The year in which daylight saving time is first observed.  This is an {@link
   * GregorianCalendar#AD AD} value.  If this value is less than 1 then daylight saving time is
   * observed for all <code>AD</code> years. <p>If <code>useDaylight</code> is false, this value is
   * ignored.
   *
   * @serial
   */
  private int startYear;

  /**
   * The offset in milliseconds between this zone and GMT.  Negative offsets
   * are to the west of Greenwich.  To obtain local <em>standard</em> time,
   * add the offset to GMT time.  To obtain local wall time it may also be
   * necessary to add <code>dstSavings</code>.
   *
   * @serial
   */
  private int rawOffset;

  /**
   * A boolean value which is true if and only if this zone uses daylight
   * saving time.  If this value is false, several other fields are ignored.
   *
   * @serial
   */
  private boolean useDaylight = false; // indicate if this time zone uses DST

  private static final int millisPerHour = 60 * 60 * 1000;
  private static final int millisPerDay = 24 * millisPerHour;

  /**
   * This field was serialized in JDK 1.1, so we have to keep it that way
   * to maintain serialization compatibility. However, there's no need to
   * recreate the array each time we create a new time zone.
   *
   * @serial An array of bytes containing the values {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30,
   * 31}.  This is ignored as of the Java 2 platform v1.2, however, it must be streamed out for
   * compatibility with JDK 1.1.
   */
  private final byte monthLength[] = staticMonthLength;
  private final static byte staticMonthLength[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
  private final static byte staticLeapMonthLength[] = {31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30,
      31};

  /**
   * Variables specifying the mode of the start rule.  Takes the following
   * values:
   * <dl>
   * <dt><code>DOM_MODE</code></dt>
   * <dd>
   * Exact day of week; e.g., March 1.
   * </dd>
   * <dt><code>DOW_IN_MONTH_MODE</code></dt>
   * <dd>
   * Day of week in month; e.g., last Sunday in March.
   * </dd>
   * <dt><code>DOW_GE_DOM_MODE</code></dt>
   * <dd>
   * Day of week after day of month; e.g., Sunday on or after March 15.
   * </dd>
   * <dt><code>DOW_LE_DOM_MODE</code></dt>
   * <dd>
   * Day of week before day of month; e.g., Sunday on or before March 15.
   * </dd>
   * </dl>
   * The setting of this field affects the interpretation of the
   * <code>startDay</code> field.
   * <p>If <code>useDaylight</code> is false, this value is ignored.
   *
   * @serial
   * @since 1.1.4
   */
  private int startMode;

  /**
   * Variables specifying the mode of the end rule.  Takes the following
   * values:
   * <dl>
   * <dt><code>DOM_MODE</code></dt>
   * <dd>
   * Exact day of week; e.g., March 1.
   * </dd>
   * <dt><code>DOW_IN_MONTH_MODE</code></dt>
   * <dd>
   * Day of week in month; e.g., last Sunday in March.
   * </dd>
   * <dt><code>DOW_GE_DOM_MODE</code></dt>
   * <dd>
   * Day of week after day of month; e.g., Sunday on or after March 15.
   * </dd>
   * <dt><code>DOW_LE_DOM_MODE</code></dt>
   * <dd>
   * Day of week before day of month; e.g., Sunday on or before March 15.
   * </dd>
   * </dl>
   * The setting of this field affects the interpretation of the
   * <code>endDay</code> field.
   * <p>If <code>useDaylight</code> is false, this value is ignored.
   *
   * @serial
   * @since 1.1.4
   */
  private int endMode;

  /**
   * A positive value indicating the amount of time saved during DST in
   * milliseconds.
   * Typically one hour (3600000); sometimes 30 minutes (1800000).
   * <p>If <code>useDaylight</code> is false, this value is ignored.
   *
   * @serial
   * @since 1.1.4
   */
  private int dstSavings;

  private static final Gregorian gcal = CalendarSystem.getGregorianCalendar();

  /**
   * Cache values representing a single period of daylight saving
   * time. When the cache values are valid, cacheStart is the start
   * time (inclusive) of daylight saving time and cacheEnd is the
   * end time (exclusive).
   *
   * cacheYear has a year value if both cacheStart and cacheEnd are
   * in the same year. cacheYear is set to startYear - 1 if
   * cacheStart and cacheEnd are in different years. cacheStart is 0
   * if the cache values are void. cacheYear is a long to support
   * Integer.MIN_VALUE - 1 (JCK requirement).
   */
  private transient long cacheYear;
  private transient long cacheStart;
  private transient long cacheEnd;

  /**
   * Constants specifying values of startMode and endMode.
   */
  private static final int DOM_MODE = 1; // Exact day of month, "Mar 1"
  private static final int DOW_IN_MONTH_MODE = 2; // Day of week in month, "lastSun"
  private static final int DOW_GE_DOM_MODE = 3; // Day of week after day of month, "Sun>=15"
  private static final int DOW_LE_DOM_MODE = 4; // Day of week before day of month, "Sun<=21"

  /**
   * Constant for a mode of start or end time specified as wall clock
   * time.  Wall clock time is standard time for the onset rule, and
   * daylight time for the end rule.
   *
   * @since 1.4
   */
  public static final int WALL_TIME = 0; // Zero for backward compatibility

  /**
   * Constant for a mode of start or end time specified as standard time.
   *
   * @since 1.4
   */
  public static final int STANDARD_TIME = 1;

  /**
   * Constant for a mode of start or end time specified as UTC. European
   * Union rules are specified as UTC time, for example.
   *
   * @since 1.4
   */
  public static final int UTC_TIME = 2;

  // Proclaim compatibility with 1.1
  static final long serialVersionUID = -403250971215465050L;

  // the internal serial version which says which version was written
  // - 0 (default) for version up to JDK 1.1.3
  // - 1 for version from JDK 1.1.4, which includes 3 new fields
  // - 2 for JDK 1.3, which includes 2 new fields
  static final int currentSerialVersion = 2;

  /**
   * The version of the serialized data on the stream.  Possible values:
   * <dl>
   * <dt><b>0</b> or not present on stream</dt>
   * <dd>
   * JDK 1.1.3 or earlier.
   * </dd>
   * <dt><b>1</b></dt>
   * <dd>
   * JDK 1.1.4 or later.  Includes three new fields: <code>startMode</code>,
   * <code>endMode</code>, and <code>dstSavings</code>.
   * </dd>
   * <dt><b>2</b></dt>
   * <dd>
   * JDK 1.3 or later.  Includes two new fields: <code>startTimeMode</code>
   * and <code>endTimeMode</code>.
   * </dd>
   * </dl>
   * When streaming out this class, the most recent format
   * and the highest allowable <code>serialVersionOnStream</code>
   * is written.
   *
   * @serial
   * @since 1.1.4
   */
  private int serialVersionOnStream = currentSerialVersion;

  synchronized private void invalidateCache() {
    cacheYear = startYear - 1;
    cacheStart = cacheEnd = 0;
  }

  //----------------------------------------------------------------------
  // Rule representation
  //
  // We represent the following flavors of rules:
  //       5        the fifth of the month
  //       lastSun  the last Sunday in the month
  //       lastMon  the last Monday in the month
  //       Sun>=8   first Sunday on or after the eighth
  //       Sun<=25  last Sunday on or before the 25th
  // This is further complicated by the fact that we need to remain
  // backward compatible with the 1.1 FCS.  Finally, we need to minimize
  // API changes.  In order to satisfy these requirements, we support
  // three representation systems, and we translate between them.
  //
  // INTERNAL REPRESENTATION
  // This is the format SimpleTimeZone objects take after construction or
  // streaming in is complete.  Rules are represented directly, using an
  // unencoded format.  We will discuss the start rule only below; the end
  // rule is analogous.
  //   startMode      Takes on enumerated values DAY_OF_MONTH,
  //                  DOW_IN_MONTH, DOW_AFTER_DOM, or DOW_BEFORE_DOM.
  //   startDay       The day of the month, or for DOW_IN_MONTH mode, a
  //                  value indicating which DOW, such as +1 for first,
  //                  +2 for second, -1 for last, etc.
  //   startDayOfWeek The day of the week.  Ignored for DAY_OF_MONTH.
  //
  // ENCODED REPRESENTATION
  // This is the format accepted by the constructor and by setStartRule()
  // and setEndRule().  It uses various combinations of positive, negative,
  // and zero values to encode the different rules.  This representation
  // allows us to specify all the different rule flavors without altering
  // the API.
  //   MODE              startMonth    startDay    startDayOfWeek
  //   DOW_IN_MONTH_MODE >=0           !=0         >0
  //   DOM_MODE          >=0           >0          ==0
  //   DOW_GE_DOM_MODE   >=0           >0          <0
  //   DOW_LE_DOM_MODE   >=0           <0          <0
  //   (no DST)          don't care    ==0         don't care
  //
  // STREAMED REPRESENTATION
  // We must retain binary compatibility with the 1.1 FCS.  The 1.1 code only
  // handles DOW_IN_MONTH_MODE and non-DST mode, the latter indicated by the
  // flag useDaylight.  When we stream an object out, we translate into an
  // approximate DOW_IN_MONTH_MODE representation so the object can be parsed
  // and used by 1.1 code.  Following that, we write out the full
  // representation separately so that contemporary code can recognize and
  // parse it.  The full representation is written in a "packed" format,
  // consisting of a version number, a length, and an array of bytes.  Future
  // versions of this class may specify different versions.  If they wish to
  // include additional data, they should do so by storing them after the
  // packed representation below.
  //----------------------------------------------------------------------

  /**
   * Given a set of encoded rules in startDay and startDayOfMonth, decode
   * them and set the startMode appropriately.  Do the same for endDay and
   * endDayOfMonth.  Upon entry, the day of week variables may be zero or
   * negative, in order to indicate special modes.  The day of month
   * variables may also be negative.  Upon exit, the mode variables will be
   * set, and the day of week and day of month variables will be positive.
   * This method also recognizes a startDay or endDay of zero as indicating
   * no DST.
   */
  private void decodeRules() {
    decodeStartRule();
    decodeEndRule();
  }

  /**
   * Decode the start rule and validate the parameters.  The parameters are
   * expected to be in encoded form, which represents the various rule modes
   * by negating or zeroing certain values.  Representation formats are:
   * <p>
   * <pre>
   *            DOW_IN_MONTH  DOM    DOW>=DOM  DOW<=DOM  no DST
   *            ------------  -----  --------  --------  ----------
   * month       0..11        same    same      same     don't care
   * day        -5..5         1..31   1..31    -1..-31   0
   * dayOfWeek   1..7         0      -1..-7    -1..-7    don't care
   * time        0..ONEDAY    same    same      same     don't care
   * </pre>
   * The range for month does not include UNDECIMBER since this class is
   * really specific to GregorianCalendar, which does not use that month.
   * The range for time includes ONEDAY (vs. ending at ONEDAY-1) because the
   * end rule is an exclusive limit point.  That is, the range of times that
   * are in DST include those >= the start and < the end.  For this reason,
   * it should be possible to specify an end of ONEDAY in order to include the
   * entire day.  Although this is equivalent to time 0 of the following day,
   * it's not always possible to specify that, for example, on December 31.
   * While arguably the start range should still be 0..ONEDAY-1, we keep
   * the start and end ranges the same for consistency.
   */
  private void decodeStartRule() {
    useDaylight = (startDay != 0) && (endDay != 0);
    if (startDay != 0) {
      if (startMonth < Calendar.JANUARY || startMonth > Calendar.DECEMBER) {
        throw new IllegalArgumentException(
            "Illegal start month " + startMonth);
      }
      if (startTime < 0 || startTime > millisPerDay) {
        throw new IllegalArgumentException(
            "Illegal start time " + startTime);
      }
      if (startDayOfWeek == 0) {
        startMode = DOM_MODE;
      } else {
        if (startDayOfWeek > 0) {
          startMode = DOW_IN_MONTH_MODE;
        } else {
          startDayOfWeek = -startDayOfWeek;
          if (startDay > 0) {
            startMode = DOW_GE_DOM_MODE;
          } else {
            startDay = -startDay;
            startMode = DOW_LE_DOM_MODE;
          }
        }
        if (startDayOfWeek > Calendar.SATURDAY) {
          throw new IllegalArgumentException(
              "Illegal start day of week " + startDayOfWeek);
        }
      }
      if (startMode == DOW_IN_MONTH_MODE) {
        if (startDay < -5 || startDay > 5) {
          throw new IllegalArgumentException(
              "Illegal start day of week in month " + startDay);
        }
      } else if (startDay < 1 || startDay > staticMonthLength[startMonth]) {
        throw new IllegalArgumentException(
            "Illegal start day " + startDay);
      }
    }
  }

  /**
   * Decode the end rule and validate the parameters.  This method is exactly
   * analogous to decodeStartRule().
   *
   * @see decodeStartRule
   */
  private void decodeEndRule() {
    useDaylight = (startDay != 0) && (endDay != 0);
    if (endDay != 0) {
      if (endMonth < Calendar.JANUARY || endMonth > Calendar.DECEMBER) {
        throw new IllegalArgumentException(
            "Illegal end month " + endMonth);
      }
      if (endTime < 0 || endTime > millisPerDay) {
        throw new IllegalArgumentException(
            "Illegal end time " + endTime);
      }
      if (endDayOfWeek == 0) {
        endMode = DOM_MODE;
      } else {
        if (endDayOfWeek > 0) {
          endMode = DOW_IN_MONTH_MODE;
        } else {
          endDayOfWeek = -endDayOfWeek;
          if (endDay > 0) {
            endMode = DOW_GE_DOM_MODE;
          } else {
            endDay = -endDay;
            endMode = DOW_LE_DOM_MODE;
          }
        }
        if (endDayOfWeek > Calendar.SATURDAY) {
          throw new IllegalArgumentException(
              "Illegal end day of week " + endDayOfWeek);
        }
      }
      if (endMode == DOW_IN_MONTH_MODE) {
        if (endDay < -5 || endDay > 5) {
          throw new IllegalArgumentException(
              "Illegal end day of week in month " + endDay);
        }
      } else if (endDay < 1 || endDay > staticMonthLength[endMonth]) {
        throw new IllegalArgumentException(
            "Illegal end day " + endDay);
      }
    }
  }

  /**
   * Make rules compatible to 1.1 FCS code.  Since 1.1 FCS code only understands
   * day-of-week-in-month rules, we must modify other modes of rules to their
   * approximate equivalent in 1.1 FCS terms.  This method is used when streaming
   * out objects of this class.  After it is called, the rules will be modified,
   * with a possible loss of information.  startMode and endMode will NOT be
   * altered, even though semantically they should be set to DOW_IN_MONTH_MODE,
   * since the rule modification is only intended to be temporary.
   */
  private void makeRulesCompatible() {
    switch (startMode) {
      case DOM_MODE:
        startDay = 1 + (startDay / 7);
        startDayOfWeek = Calendar.SUNDAY;
        break;

      case DOW_GE_DOM_MODE:
        // A day-of-month of 1 is equivalent to DOW_IN_MONTH_MODE
        // that is, Sun>=1 == firstSun.
        if (startDay != 1) {
          startDay = 1 + (startDay / 7);
        }
        break;

      case DOW_LE_DOM_MODE:
        if (startDay >= 30) {
          startDay = -1;
        } else {
          startDay = 1 + (startDay / 7);
        }
        break;
    }

    switch (endMode) {
      case DOM_MODE:
        endDay = 1 + (endDay / 7);
        endDayOfWeek = Calendar.SUNDAY;
        break;

      case DOW_GE_DOM_MODE:
        // A day-of-month of 1 is equivalent to DOW_IN_MONTH_MODE
        // that is, Sun>=1 == firstSun.
        if (endDay != 1) {
          endDay = 1 + (endDay / 7);
        }
        break;

      case DOW_LE_DOM_MODE:
        if (endDay >= 30) {
          endDay = -1;
        } else {
          endDay = 1 + (endDay / 7);
        }
        break;
    }

        /*
         * Adjust the start and end times to wall time.  This works perfectly
         * well unless it pushes into the next or previous day.  If that
         * happens, we attempt to adjust the day rule somewhat crudely.  The day
         * rules have been forced into DOW_IN_MONTH mode already, so we change
         * the day of week to move forward or back by a day.  It's possible to
         * make a more refined adjustment of the original rules first, but in
         * most cases this extra effort will go to waste once we adjust the day
         * rules anyway.
         */
    switch (startTimeMode) {
      case UTC_TIME:
        startTime += rawOffset;
        break;
    }
    while (startTime < 0) {
      startTime += millisPerDay;
      startDayOfWeek = 1 + ((startDayOfWeek + 5) % 7); // Back 1 day
    }
    while (startTime >= millisPerDay) {
      startTime -= millisPerDay;
      startDayOfWeek = 1 + (startDayOfWeek % 7); // Forward 1 day
    }

    switch (endTimeMode) {
      case UTC_TIME:
        endTime += rawOffset + dstSavings;
        break;
      case STANDARD_TIME:
        endTime += dstSavings;
    }
    while (endTime < 0) {
      endTime += millisPerDay;
      endDayOfWeek = 1 + ((endDayOfWeek + 5) % 7); // Back 1 day
    }
    while (endTime >= millisPerDay) {
      endTime -= millisPerDay;
      endDayOfWeek = 1 + (endDayOfWeek % 7); // Forward 1 day
    }
  }

  /**
   * Pack the start and end rules into an array of bytes.  Only pack
   * data which is not preserved by makeRulesCompatible.
   */
  private byte[] packRules() {
    byte[] rules = new byte[6];
    rules[0] = (byte) startDay;
    rules[1] = (byte) startDayOfWeek;
    rules[2] = (byte) endDay;
    rules[3] = (byte) endDayOfWeek;

    // As of serial version 2, include time modes
    rules[4] = (byte) startTimeMode;
    rules[5] = (byte) endTimeMode;

    return rules;
  }

  /**
   * Given an array of bytes produced by packRules, interpret them
   * as the start and end rules.
   */
  private void unpackRules(byte[] rules) {
    startDay = rules[0];
    startDayOfWeek = rules[1];
    endDay = rules[2];
    endDayOfWeek = rules[3];

    // As of serial version 2, include time modes
    if (rules.length >= 6) {
      startTimeMode = rules[4];
      endTimeMode = rules[5];
    }
  }

  /**
   * Pack the start and end times into an array of bytes.  This is required
   * as of serial version 2.
   */
  private int[] packTimes() {
    int[] times = new int[2];
    times[0] = startTime;
    times[1] = endTime;
    return times;
  }

  /**
   * Unpack the start and end times from an array of bytes.  This is required
   * as of serial version 2.
   */
  private void unpackTimes(int[] times) {
    startTime = times[0];
    endTime = times[1];
  }

  /**
   * Save the state of this object to a stream (i.e., serialize it).
   *
   * @serialData We write out two formats, a JDK 1.1 compatible format, using
   * <code>DOW_IN_MONTH_MODE</code> rules, in the required section, followed by the full rules, in
   * packed format, in the optional section.  The optional section will be ignored by JDK 1.1 code
   * upon stream in. <p> Contents of the optional section: The length of a byte array is emitted
   * (int); this is 4 as of this release. The byte array of the given length is emitted. The
   * contents of the byte array are the true values of the fields <code>startDay</code>,
   * <code>startDayOfWeek</code>, <code>endDay</code>, and <code>endDayOfWeek</code>.  The values of
   * these fields in the required section are approximate values suited to the rule mode
   * <code>DOW_IN_MONTH_MODE</code>, which is the only mode recognized by JDK 1.1.
   */
  private void writeObject(ObjectOutputStream stream)
      throws IOException {
    // Construct a binary rule
    byte[] rules = packRules();
    int[] times = packTimes();

    // Convert to 1.1 FCS rules.  This step may cause us to lose information.
    makeRulesCompatible();

    // Write out the 1.1 FCS rules
    stream.defaultWriteObject();

    // Write out the binary rules in the optional data area of the stream.
    stream.writeInt(rules.length);
    stream.write(rules);
    stream.writeObject(times);

    // Recover the original rules.  This recovers the information lost
    // by makeRulesCompatible.
    unpackRules(rules);
    unpackTimes(times);
  }

  /**
   * Reconstitute this object from a stream (i.e., deserialize it).
   *
   * We handle both JDK 1.1
   * binary formats and full formats with a packed byte array.
   */
  private void readObject(ObjectInputStream stream)
      throws IOException, ClassNotFoundException {
    stream.defaultReadObject();

    if (serialVersionOnStream < 1) {
      // Fix a bug in the 1.1 SimpleTimeZone code -- namely,
      // startDayOfWeek and endDayOfWeek were usually uninitialized.  We can't do
      // too much, so we assume SUNDAY, which actually works most of the time.
      if (startDayOfWeek == 0) {
        startDayOfWeek = Calendar.SUNDAY;
      }
      if (endDayOfWeek == 0) {
        endDayOfWeek = Calendar.SUNDAY;
      }

      // The variables dstSavings, startMode, and endMode are post-1.1, so they
      // won't be present if we're reading from a 1.1 stream.  Fix them up.
      startMode = endMode = DOW_IN_MONTH_MODE;
      dstSavings = millisPerHour;
    } else {
      // For 1.1.4, in addition to the 3 new instance variables, we also
      // store the actual rules (which have not be made compatible with 1.1)
      // in the optional area.  Read them in here and parse them.
      int length = stream.readInt();
      byte[] rules = new byte[length];
      stream.readFully(rules);
      unpackRules(rules);
    }

    if (serialVersionOnStream >= 2) {
      int[] times = (int[]) stream.readObject();
      unpackTimes(times);
    }

    serialVersionOnStream = currentSerialVersion;
  }
}
